As an international relations major (pol.sci), I require 14 credit hours of a language. Beyond that, I need to become fluent, and my language is Japanese. I reccomend taking a course. I learned a lot of things myself only to find that there were many things I was doing wrong (especially in the actual writing of many kanji).
Ah, make a lot of flash cards. I keep hundreds of flashcards, and when I want to practice I just pick up a random bunch and start drilling. Also, hit up a local asian store and try to read Japanese newspapers, highlighting what you don't know (or, in my case, what you do know

).
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